The move sets up a contentious re-election fight between Cochran
and conservative groups that have made him a prime target in the
Republican primary. Cochran, who turns 76 this weekend, will face
41-year-old rising conservative star and state Sen. Chris
McDaniel, who has already snagged endorsements from the Club for
Growth and the Senate Conservatives Fund.

"Republicans in Mississippi have a real choice for the
United States Senate this year. They can vote for Senator
Cochran, or they can vote for a more fiscally conservative
alternative who is dedicated to limited government and passing
policies that will increase economic growth," Club for Growth
President Chris Chocola said in a statement.

"The Club for Growth PAC believes that State Senator Chris
McDaniel is a constitutional conservative who will fight to
repeal ObamaCare, cut spending, and stop President Obama’s
reckless agenda. The Club for Growth PAC looks forward to
strongly supporting his candidacy for the United States
Senate."

According to the latest campaign filings, Cochran has
raised less than $1 million for his re-election campaign,
prompting speculation that he was leaning toward
retirement.

Now, he becomes a huge target for conservatives, and joins
Senate Minority Leader Mitch McConnell (R-Ky.) and at least five
other GOP incumbents facing a primary challenge.

Before the practice was banned in 2010, Cochran was known
in the Senate as someone who steered a lot of federal money to
Mississippi through earmarks. Part of McDaniel's campaign will be
to emphasize the anti-spending attitude that has prevailed in the
Tea Party since its inception.

Right after news broke of Cochran's announcement,
McDaniel's official account tweeted this: